Inductors are used in circuits to help regulate current flow through the circuit. When a current flows through the inductor, energy is stored temporarily in a magnetic field in the inductor. When the current flowing through the inductor changes, a time-varying magnetic field within the inductor induces a voltage in the inductor which opposes the change in current that created the magnetic field.
As technology nodes shrink, circuit sizes are reduced. Inductors occupy a large area in a circuit design. As the circuit size decreases, proximity between the inductor or capacitor and the other devices increases. Furthermore, as metal lines in these components decrease in size, a resistance in the metal lines increases. The increased resistance in turn lowers the quality (Q) factor of the inductors. In addition, inductors cause a magnetic flux to pass through the circuit. The magnetic flux is capable of introducing noise into other devices within the circuit.